1. Field of the Invention
The present invention relates to the field of imaging, graphic imaging, print imaging, liquid ink imaging and the like. The technology is more narrowly applicable to digital imaging, particularly black-and-white or multi-color imaging.
2. Background of the Art
There are many different formats of imaging and particularly printed imaging available in commercial practice and theoretic investigation. The original forms of printing were by the physical application (by hand, stick or brush) of inks or paints to surfaces in a desired pattern or image. It wasn't until brief centuries ago that mechanical imaging came into existence, first by woodcutting a relief, applying inks to the relief image and then transferring the ink from the relief to a receiving surface by physical contact of the relief and the surface. In the Fifteenth Century, moveable type was first constructed, using the individual type settings to form a relief image for press printing of images.
A common form of personal and commercial imaging available today falls within the generic class of electrography, which includes electrophotography. In these systems, by various means, an imagewise distribution of electrostatic charges (a latent image) is formed on an image receiving surface, and an ink or toner is presented in the vicinity of the surface. At least one visible, image-forming component of the ink or toner is differentially attractive to the image receiving surface based upon the charge distribution, and an intermediate or final image is formed upon stabilization (e.g., adhesion, fusion, drying, transfer, etc.) of the deposited image onto a surface. Various background descriptions of electrophotography and particular aspects thereof are disclosed, by way of non-limiting examples, in U.S. Pat. Nos. 6,828,358; 6,815,132; 6,806,013; 6,785,495; 6,696,209; and 6,670,085, which patents are incorporated herein by reference in their entirety.
There are many different ways of forming a latent image that can be subsequently treated to provide a visible image. The various technologies for forming latent images that are toned (as opposed to latent images that are developed from materials and composition that create and store the latent image, as in photography, thermography, photothermography, diazotype and the like) may, by way of non-limiting examples, include charge application by styli, charge application by physical transfer of charges, and charge distribution formed by selective discharging to leave a distribution of residual charge. The last process is most common in the electrophotographic process. A highly simplified description of electrophotography is that a charge is (uniformly) distributed over a surface, the charged surface is exposed to a distribution of radiation (usually visible light, infrared radiation and/or UV radiation, hereinafter generally referred to as “light”), the light instigates a change in local electrical conductivity, and charge is locally carried away because of the local changes in conductivity. By removing charge is areas struck by light, a latent image of charge remains on the surface in areas that are not struck by light. This latent image is then exposed to toner or ink (usually under a biasing voltage to provide mass transfer forces for the ink or toner components) to develop the latent image, either in a positive sense or a negative sense with respect to the latent image.
U.S. Pat. No. 6,388,693 (Loos) describes an apparatus for printing graphic images on sheet material comprising a print head, such as a thermal print head having a linear array of heating elements, which is pressed into engagement with an ink web overlying the sheet material on a platen. The platen may be, for example, a roller platen which is rotatably driven to in turn drive the sheet material with the ink web relative to the print head. A removable cassette having a predetermined length L of ink web bearing a printing ink is mounted adjacent to the print head with the ink web interposed between the sheet material and the print head for printing the graphic images on the sheet. A supply spool carrying the ink web is rotatably mounted within the cassette, and a take-up spool is also rotatably mounted within the cassette for receiving the ink web from the supply spool upon passage between the platen and print head. The take-up spool defines a first overall diameter D1 without receiving the ink web from the supply spool, and a greater second overall diameter D2 upon receiving the predetermined length L of ink web, wherein the second overall diameter D2 is within approximately 10% of the first overall diameter D1. The apparatus further comprises means for applying a constant torque to the take-up spool, preferably a spring-wrapped clutch, to thereby maintain a substantially constant tension within the ink web during printing operations.
U.S. Pat. No. 5,847,733 (Bern) describes an image recording apparatus in which charged particles are deposited in an image configuration on an information carrier. The method includes conveying the charged particles to a particle source adjacent to a back electrode; positioning a particle receiving information carrier between the back electrode and the particle source; providing a control array of control electrodes; providing at least one set of deflection electrodes; creating an electric potential difference between the back electrode and the particle source to apply an attractive force on the charged particles; connecting variable voltage sources to the control electrodes to produce a pattern of electrostatic fields to at least partially open or close passages in each electrostatic field by influencing the attractive force from the back electrode, thus permitting or restricting the transport of charged particles towards the information carrier; and connecting at least one deflection voltage source to at least one set of deflection electrodes to produce deflection forces modifying the symmetry of the electrostatic fields, thus controlling the trajectory of attracted charged particles.
U.S. Pat. No. 4,630,074 (Hironouchi et al.) describes an electrode for discharge printing in accordance with an applied electrical signal comprising: (a) a multiple-stylus electrode body formed of an insulating material consisting mainly of a resin having a thermal deforming temperature at least 200° C.; and (b) several electrode elements each composed of an elongate core of a high melting point material coated with a borosiloxane resin, wherein the electrode elements are arranged in a parallel array and each has a first end moulded within said electrode body, and a second end projecting from said electrode body and laterally spaced from the second ends of the other electrode elements.
U.S. Pat. No. 4,525,727 (Kohashi) describes an electroosmotic ink printer comprising a head having an array of recording electrodes successively arranged to define a print line along one edge of the head. A common electrode is provided in spaced overlying relation with the recording electrodes. Between the electrode array and the common electrode is a means for electroosmotically moving ink in a direction toward the print line and in an opposite direction depending on an electrical potential applied to the recording electrodes with respect to the common electrode. A memory stores a video input signal in a plurality of storage locations corresponding to the recording electrodes for delivery in parallel form to a modulator for generating individual recording signals corresponding to the recording electrodes. Control means activates first and second groups of the recording electrodes by successively applying the individual recording signals thereto to cause the ink to move to the print line and deactivates the remainder of the recording electrodes by successively applying a deactivating potential to the electrodes of the group other than those to which the recording signals are applied.
U.S. Pat. No. 3,950,760 (Rausch) teaches a device for writing with liquid ink in which the transfer of the ink to the record carrier is electrically controlled. The device comprises an elongated flexible beam having a major axis extending in the direction of elongation. The beam includes a piezoelectric element and electrodes. The element is made of a piezoelectric material having at least two regions oppositely polarized. The regions are disposed to bend the beam in a direction transverse to the major axis of the beam responsive to an associated electric potential applied to the electrodes. The beam further includes electrodes disposed on the surface of the element. The element includes walls defining a plurality of ducts which extend in the longitudinal direction of the beam. The device includes a writing stylus secured to the end face of the beam. The stylus includes means for conveying liquid ink, the means being in fluid communication with at least one of the ducts.
U.S. Pat. No. 4,406,603 (Goffe) describes an apparatus for applying a charge pattern to an insulating imaging member by a stylus array of the type wherein the styli of the array are in direct contact with the insulating imaging member, and the insulating imaging member and the styli move relatively with respect to each other, the improvement comprising: an adjustable stylus array having each stylus in the array resiliently held into contact with the insulating imaging member; means for applying a signal voltage to the styli in said array for production of a charge pattern on the insulating imaging member; and means for adjusting said stylus array to obtain a force of contact between the styli in the array and the insulating imaging member that is below the force of contact necessary to develop a triboelectric charge on the insulating imaging member because of the rubbing contact with the styli during relative movement between the styli and the insulating imaging member, so that there will be substantially no background charge on the insulating imaging member.
Other electrographic systems with stylus-generated latent images include, by way of non-limiting examples, U.S. Pat. Nos. 5,663,024; 5,732,311; 5,753,763; and 6,008,627.
These systems are capable of providing high quality images, but a concern with many of the electrophotographic systems is a lack of speed because of the need for raster scanning of the image by collimated radiation (e.g., a laser) to effect the distribution of discharged areas on the surface where toner or ink is to be deposited. This step is inherently a rate controlling step in the process as it is a physical step where the collimated radiation covers only a small area (the laser spot), and that spot must be physically moved over the entire image surface, one spot at a time to construct pixels on the surface. Any process that could further speed up a toned imaging process would be desirable.